fmod

 

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Type-generic math

 

Common mathematical functions

Functions
Basic operations
abslabsllabsimaxabs (C99) fabs divldivlldivimaxdiv (C99) fmod	remainder (C99) remquo (C99) fma (C99) fmax (C99) fmin (C99) fdim (C99) nannanfnanl (C99)(C99)(C99)
Exponential functions
exp exp2 (C99) expm1 (C99)	log log10 log1p (C99) log2 (C99)
Power functions
sqrt cbrt (C99)	hypot (C99) pow
Trigonometric and hyperbolic functions
sin cos tan asin acos atan atan2	sinh cosh tanh asinh (C99) acosh (C99) atanh (C99)
Error and gamma functions
erf (C99) erfc (C99)	lgamma (C99) tgamma (C99)
Nearest integer floating point operations
ceil floor roundlroundllround (C99)(C99)(C99)	trunc (C99) nearbyint (C99) rintlrintllrint (C99)(C99)(C99)
Floating point manipulation functions
ldexp scalbnscalbln (C99)(C99) ilogb (C99) logb (C99)	frexp modf nextafternexttoward (C99)(C99) copysign (C99)
Classification
fpclassify (C99)
isfinite (C99)
isinf (C99)
isnan (C99)
isnormal (C99)
signbit (C99)
Macro constants
HUGE_VALFHUGE_VALHUGE_VALL (C99)(C99)	FP_NORMALFP_SUBNORMALFP_ZEROFP_INFINITEFP_NAN (C99)(C99)(C99)(C99)(C99)

 

Defined in header <math.h>
float       fmodf( float x, float y );		(since C99)
double      fmod( double x, double y );
long double fmodl( long double x, long double y );		(since C99)

Computes the remainder of the division operation x/y.

Specifically, the returned value is x - n*y, where n is x/y with its fractional part truncated.

The returned value will have the same sign as x.

Parameters

x, y

-

floating point values

Return value

Remainder of dividing arguments. The returned value will have the same sign as x.

Example

fmod <-- 5.1 - (5.1/3.0) * 3.0
         5.1 - (1.7)     * 3.0
         5.1 - (1.0)     * 3.0  (fractional part truncated)
         5.1 - 3.0
         2.1

Run this code

#include <stdio.h>
#include <math.h>
 
int main()
{ 
    printf("fmod(+5.1,+3.0) = %+.1f\n", fmod(+5.1,+3.0));
    printf("fmod(-5.1,+3.0) = %+.1f\n", fmod(-5.1,+3.0));
    printf("fmod(+5.1,-3.0) = %+.1f\n", fmod(+5.1,-3.0));
    printf("fmod(-5.1,-3.0) = %+.1f\n", fmod(-5.1,-3.0));
 
    return 0;
}

Output:

fmod(+5.1,+3.0) = +2.1
fmod(-5.1,+3.0) = -2.1
fmod(+5.1,-3.0) = +2.1
fmod(-5.1,-3.0) = -2.1

See also

divldivlldivimaxdiv (C99)	the quotient and remainder of integer division (function)
remainder (C99)	signed remainder of the division operation (function)
C++ documentation for fmod